Changchun Yin

• Professor
• Professor at Jilin University

When using electrical prospecting methods to monitor the front edge of waterflooding in the residual oil development, the electromagnetic responses generated by the high conductivity of the steel casing in the observation area usually obscure the electrical abnormal signal of the formation caused by waterflooding, largely affecting the imaging accu...

As an effective geophysical tool, ground penetrating radar (GPR) is widely used for environmental and engineering detections. Numerous numerical simulation algorithms have been developed to improve the computational efficiency of GPR simulations, enabling the modeling of complex structures. The discontinuous Galerkin method is a high efficiency num...

Bauxite plays a crucial role in metallic and non-metallic industry. The surface-exposed salento-type bauxite deposits have been largely exploited and developed. With the increasing demand of these resources, it is important but very challenging to explore the potential bauxite deposits in the deep earth. In this paper, based on new developments in...

The mantle transition zone (MTZ) plays a key role in the deep global material cycle, while the water content in MTZ is debated from saturated to dry. Since the electrical conductivity is highly sensitive to water, its accurate estimation will greatly help reveal the water content. High-quality and plenty of data are crucial for global-scale conduct...

As the structure of the underground space becomes increasingly complex, traditional two-dimensional seismoelectric methods are no longer adequate for the comprehensive exploration. To achieve precise imaging of the underground space, it is in urgent need to develop three-dimensional full-waveform modeling techniques. In this paper, we propose a thr...

Airborne electromagnetic (AEM) technology is an efficient geophysical exploration tool for investigating subsurface electrical structures. In recent years, 3D inversion of AEM data is being developed rapidly, but it still faces challenges such as low resolution and computational efficiency. To solve these problems, we propose a multiscale shearlet-...

Satellite magnetic data contain significant information about the Earth’s interior electrical structure. However, the altitudes of satellites vary over time and latitude. Theoretically, the signals from the external magnetosphere and ionosphere, along with the induced magnetic field from the Earth, exhibit considerable variation at different altitu...

Previous works have demonstrated that inverting MT data jointly with gravity data can synergize the high lateral resolution of gravity and the vertical resolution of MT. However, the existing joint stabilizers usually work for structured grids instead of unstructured ones that are more powerful for characterizing complex geology. Here, we utilize L...

Slow forward modeling is the main factor that restricts the practical use of three-dimensional (3D) inversion and interpretation of airborne electromagnetic (AEM) data. To improve the modeling efficiency in 3D AEM, we propose a new multiscale finite-element (MsFE) method based on unstructured hexahedral meshes. Compared with the traditional 3D AEM...

At present, the mainstream technology for leachate detection in landfills is electrical resistivity tomography (ERT), known for its efficiency and non-destructive nature. However, the conventional ERT data interpretation primarily uses inversion based on structured grids, which cannot accurately simulate the complex and thin impermeable layers of l...

In this paper, we propose a 3D MT inversion method based on equivalent transformation, in which the forward modeling is executed by the finite-element (FE) method based on the dense unstructured mesh, while for the inversion the model space is transformed to the element nodes. A spatial mapping is constructed to achieve 3D MT inversions with model...

We develop a new spectral-element method (SEM) by incorporating a domain-decomposition technique, referred to as the dual-primal spectral-element tearing and interconnecting method (SETI-DP), for high-precision forward simulation of three-dimensional (3D) DC resistivity method. To handle the terrain and complex underground structures, we use unstru...

In mineral, environmental, and engineering explorations, we frequently encounter geological bodies with varied sizes, depths, and conductivity contrasts with surround rocks and try to interpret them with single survey data. The conventional three-dimensional (3-D) inversions significantly rely on the size of the grids, which should be smaller than...

The water content in the Earth’s interior is of great significance for material circulation and the dynamic evolution of the planet. The water content in mantle minerals significantly affects their conductivities. By measuring the variations in conductivity within the Earth, we can infer the water content in the mantle and study the movement and pr...

Many mineral deposits demonstrate low-resistivity characteristics. This property makes the electromagnetic (EM) method a very useful tool for mineral exploration. In the past decades, the application of EM exploration technologies has been reviewed in many case studies. However, most reviews focused on EM exploration methods, the development of equ...

The conventional geo-electromagnetic data inversions are mostly based on the gradient optimization methods. However, this type of methods can only provide single “optimal” inverse model under specific prior conditions, which cannot effectively evaluate the reliability and uncertainty of the inversion results. The widely used uncertainty quantificat...

Marine controlled-source electromagnetic (MCSEM) inversion plays a crucial role in hydrocarbon exploration and pre-drill reservoir evaluation. Deep learning techniques have been widely used in geophysical inversions. Although they work on theoretical data well, their performance on survey data needs to be improved. Since no constraint of physical l...

We propose a novel method for 3-D magnetotelluric (MT) forward modelling based on hybrid meshless and finite-element (FE) methods. This method divides the earth model into a central computational region and an expansion one. For the central region, we adopt scatter points to discretize the model, which can flexibly and accurately characterize the c...

The airborne electromagnetic (AEM) method can be used to effectively explore underground conductivity structures at high resolution. Conventional three-dimensional (3D) AEM inversions are mainly based on gradient-type deterministic methods; however, their results cannot be evaluated without bias because they only provide an updated model from an in...

Airborne electromagnetic (AEM) surveys usually covers a large area and create a large amount of data. This has limited the application of three-dimensional (3D) AEM inversions. To make 3D AEM data inversion at a large scale possible, the local mesh method has been proposed to avoid solving large matrix equations in 3D AEM modeling. However, the loc...

The choice of data misfit measure has a great impact on the convergence of electromagnetic (EM) inversion. The conventional measure based on the $l_{2}$ -norm tends to excessively amplify the weights of a larger misfit, inadvertently neglecting data with a smaller misfit during the inversion process, thereby diminishing the resolution to a certai...

A time-domain finite-element method based on an arbitrary quadrilateral mesh is pro-posed to simulate two dimensional seismoelectric and electroseismic waves in SHTEmode. By decoupling the electrokinetic coupling equation, we can solve seismic wavesand electromagnetic waves independently. For the simulation of seismic wavefield, weutilize a more co...

In fractal, porous, and cranny rough media, the diffusion of the electromagnetic (EM) field differs from that in piecewise smooth media. This phenomenon is known as an anomalous diffusion. To study the influence of anomalous diffusion on EM signals, we use the fractional time derivative and derive a governing equation describing the subdiffusion pr...

Landslides are common geological hazards that often result in significant casualties and economic losses. Due to their occurrence in complex terrain areas, conventional geophysical techniques face challenges in early detection and warning of landslides. Semi-airborne electromagnetic (SAEM) technology, utilizing unmanned aerial platforms for rapid u...

The study of the numerical simulation of seismoelectric effects is very helpful for understanding the theory and mechanism of seismoelectric activities. Quasi-static approximation is widely used in the numerical simulation of seismoelectric fields. However, numerical errors occur when the model domain is not within the near-field area of EM waves o...

The finite-element (FE) method for three-dimensional (3D) airborne electromagnetic (AEM) modeling can flexibly simulate complex geological structures at high accuracy. However, it has low efficiency and high computational requirements. To solve these problems, one needs to generate meshes more reasonably. In view of this, we develop an adaptive oct...

We propose a novel smoothing regularization scheme for three-dimensional (3D) magnetotelluric (MT) inversion based on unstructured tetrahedral discretization. Different from conventional methods that explicitly add smoothing constraints to model parameters, we choose to do the gradient filtering to smooth the model updates in an implicit way. By tr...

The flight altitude has a large effect on the airborne electromagnetic (AEM) responses. Due to the dynamic environment of the aircraft, the recorded sensor altitudes may contain errors. Research demonstrates that the AEM responses caused by a several meters altitude errors can be larger than caused by some anomalous body. Ignoring these errors will...

The surface-to-borehole transient electromagnetic (SBTEM) method can provide images at higher resolution for deep earth because its receivers are close to targets. However, as usually the boreholes distribute sparsely, the limited EM data can result in an “equivalent trap” in SBTEM inversions, i.e., the data are well-fitted, but the model is not pr...

Airborne electromagnetic (AEM) exploration produces large amounts of data due to its high sampling rate, so that the three-dimensional (3D) inversions take extremely big computation and time consumption. We present a fast 3D inversion framework for large-scale AEM explorations using a preconditioned stochastic gradient descent combined with Gauss-N...

The traditional three-dimensional (3D) magnetotelluric (MT) forward modeling using Krylov subspace algorithms has the problem of low modeling efficiency. To improve the computational efficiency of 3D MT forward modeling, we present a novel geometric multigrid algorithm for the finite element method. We use the vector finite element to discretize Ma...

As an efficient geophysical exploration tool, the airborne electromagnetic (AEM) method has been widely used in mineral exploration, geological mapping, environmental and engineering investigation, etc. Currently, the imaging and 1D inversions are the mainstream means for AEM interpretation as the amount of AEM data is huge and 2D and 3D inversions...

The conventional magnetotelluric (MT) data inversion methods, such as the nonlinear conjugate gradient method, quasi-Newton method, and Gauss-Newton method and so on, can converge robustly, but their results are easily affected by the initial model and regularization term. Although supervised learning can break through the resolution limitation by...

Bayesian inversion of electromagnetic data can obtain key information on the uncertainty of subsurface resistivity. However, due to its high computational cost, Bayesian inversion is largely limited to 1D resistivity models. In this study, a fast Bayesian inversion method is implemented by introducing the spatial correlation as prior information. T...

In a heterogeneous medium (usually called a rough medium) with fractured formations, the propagation of an electromagnetic (EM) field is a type of subdiffusion. Current mainstream geophysical EM data processing methods cannot be applied to data acquired on heterogeneous earth, as they are not governed by the classic diffusion theory. To evaluate th...

As an efficient geophysical exploration method, the time-domain airborne electromagnetic (AEM) data often show sign reversal in late-time channels due to induced polarization (IP) effect. The traditional imaging and inversion methods without considering the IP effect cannot recover the true electrical structure of the earth, so it is necessary to d...

The seismoelectric effect is a coupling phenomenon between the seismic wave field and electromagnetic field caused by the electric double layer in a fluid-saturated porous medium. As seismoelectric signals are sensitive to porous medium properties, such as the water saturation, salinity, porosity, and permeability, they have good potential for imag...

Domain decomposition approach is effective in converting large modeling problems into many small ones, so that the parallel computation can be easily facilitated and the memory consumption can be largely reduced. In this paper, we developed a domain-decomposition method for 3D time-domain marine controlled-source (MCSEM) modeling based on Dual-Prim...

Gravity inversion is a typical geophysical inversion method that obtains the underground density distribution by analyzing the gravity anomaly. Normally, it can be divided into geophysics-based and deep learning based inversion. The 3D geophysics-based inversion is a time- and memory-consuming method, so 3D inversion is not routinely implemented in...

We propose a new three‐dimensional anisotropic inversion scheme for magnetotelluric (MT) data. In this method, the earth is discretized into unstructured tetrahedral grids that can fit complex structures well, such as the earth topography and coastline. We use a 3 × 3 tensor to describe the anisotropic conductivity in the governing equation for MT...

Three dimensional gravity inversion is an effective way to extract subsurface density distribution from gravity data. Different from the conventional geophysics-based inversions, machine-learning-based inversion is a data-driven method mapping the observed data to a 3D model. We have developed a new machine-learning-based inversion method by establ...

The manuscript was processed without taking into account the authors’ modifications based on the last comments of reviewers, mainly in-text citations. These have now been added to the original article.

Three-dimensional (3D) airborne electromagnetic (AEM) inversions have been restricted by the modeling efficiency resulted from the complex geology in exploration areas and massive amount of data collected by AEM systems. In order to improve the modeling efficiency, we develop an algorithm that combines the hexahedral vector finite-element (FE) with...

Based on the spatial structure correlation in different geophysical parameters, we propose a new three-dimensional (3D) joint inversion method for frequency-domain airborne electromagnetic (AEM) and airborne magnetic (AirMag) data by incorporating a local Pearson correlation constraint (LPCC). For each iteration, the entire model is separated into...

Z-axis tipper electromagnetic (ZTEM) technique is an airborne electromagnetic method that detects anomalies in the deep earth that are induced by natural sources. Conven- tional ZTEM forward modeling is generally conducted using structured grids that have limited accuracy and cannot be used to invert complex underground structures and topography. H...

Spontaneous coal combustion is a serious hazard that affects mining safety. Since the coal seams are thin and their resistivity dramatically changes during spontaneous combustion, locating the burned cavities or caving zones using electromagnetic (EM) methods is challenging. The conventional transient electromagnetic (TEM) method with a loop transm...

We present a wavelet finite-element method (WFEM) based on B-spline wavelets on the interval (BSWI) for three-dimensional (3D) frequency-domain airborne EM modeling using a secondary coupled-potential formulation. The BSWI, which is constructed on the interval (0, 1) by joining piecewise B-spline polynomials between nodes together, has proved to ha...

The spectral-element (SE) method, which is based on the Galerkin technique, has been gradually implemented in geophysical electromagnetic (EM) three-dimensional (3D) simulation. The accuracy and efficiency of this approach, implemented for both deformed hexahedral and regular meshes, has been verified for airborne EM forward modeling. One advantage...

Airborne electromagnetic (AEM) methods have been more and more widely used in mineral exploration, environmental and engineering studies, and ground water investigation. However, compared with ground-based electromagnetic (EM) methods, such as magnetotelluric or controlled-source EM, AEM methods generally produce large amount of data, which leads t...

With geophysical surveys evolving from traditional 2D to 3D models, the large volume of data adds challenges to inversion, especially when aiming to resolve complex 3D structures. An iterative forward solver for a controlled-source electromagnetic method (CSEM) requires less memory than that for a direct solver; however, it is not easy to iterative...

The conventional, L2-norm-based, regularization term in electromagnetic (EM) inversions implements smooth constraints on model complexity in the space domain, which can smoothen the boundaries of complex underground structures. To improve the resolution of 3-D frequency-domain airborne EM (AEM) inversions, we propose a new algorithm for sparse-regu...

The conventional 3D magnetotelluric (MT) forward modeling and inversions generally assume an isotropic earth model. However, wrong results can be obtained when using an isotropic model to interpret the data influenced by the anisotropy. To effectively model and recover the earth structures including anisotropy, we develop a 3D MT inversion framewor...

The conventional trans-dimensional Bayesian inversion uses Monte Carlo method to search the model space for a solution that satisfies both the acceptance probability and data fitting. With this method one can get the inverse model based on the maximum probability and determine the model uncertainty. However, because the search space is too big, the...

Rocks and ores in nature usually appear macro-anisotropic, especially in sedimentary areas with strong layering. This anisotropy will lead to false interpretation of electromagnetic (EM) data when inverted under the assumption of an isotropic earth. However, the time-domain (TD) airborne EM (AEM) inversion for an anisotropic model has not attracted...

Airborne electromagnetic (AEM) method uses aircraft as a carrier to tow EM instruments for geophysical survey. Because of its huge amount of data, the traditional AEM data inversions take one-dimensional (1D) models. However, the underground earth is very complicated, the inversions based on 1D models can frequently deliver wrong results, so that t...

The topography has serious effects on time-domain airborne electromagnetic (AEM) signal, and the EM responses resulted from the topography frequently overwhelm those from the underground abnormal bodies. This brings big challenges to the traditional AEM interpretations based on a flat ground model. In this article, we develop a 3-D AEM inversion al...

Due to the huge amount of data generated by time-domain airborne EM (AEM) systems, conductivity depth imaging methods are widely used to help in the interpretation of this data as they can be generated quickly and easily. We present a new imaging method generated using a deep neural network (DNN). The network structure combines four convolutional n...

As an important branch of geophysical exploration method, the electromagnetic method with artificial source has advanced rapidly in the past decade. These methods are classified as airborne electromagnetic method, ground-air electromagnetic method, ground electromagnetic method, and marine electromagnetic method. Over the years, researchers in Chin...

S U M M A R Y In this paper, we propose a spectral element method (SEM) based on unstructured tetrahedral grids for direct current (dc) resistivity modelling. Unlike the tensor-product of 1-D Gauss-Lobatto-Legendre (GLL) quadrature in conventional SEM, we use Proriol-Koornwinder-Dubiner (PKD) polynomials to form the high-order basis polynomials on...

The spectral element method (SEM) based on high-order complete orthogonal polynomials is an accurate and efficient numerical method for electromagnetic modelling due to its spectral accuracy and exponential convergence. The SEM combines the flexibility of the finite-element method and the high accuracy of the spectral method. In this paper, we intr...

S U M M A R Y We introduce a novel block rational Krylov method to accelerate 3-D time-domain marine controlled-source electromagnetic modelling with multiple sources. This method approximates the time-varying electric solutions explicitly in terms of matrix exponential functions. A main attraction is that no time stepping is required, while most o...

The unstructured finite-element method has been widely used in 3D time-domain electromagnetic (EM) modeling due to its flexibility for modeling rugged topography and complex underground structures. However, how to generate high-quality grids becomes the key to high-accuracy EM responses. We have developed a weighted goal-oriented adaptive finite-el...

S U M M A R Y The transient electromagnetic (TEM) data acquired in mountainous area are seriously affected by topography, implying that consideration of topographic effect in the interpretation is in urgent need. To deal with this problem, we propose a new method to invert TEM data by simulating the topography. The unstructured tetrahedral grid wit...

This paper presents a 3D forward modelling algorithm with an adaptive finite-element method based on unstructured grids that when used with a circular scanning DC measurement technique can provide an indication of anisotropy in a layered earth. The accuracy of this algorithm is checked against 1D semi-analytical solutions for an arbitrarily anisotr...

We investigate an algorithm for 3D time-domain AEM inversion with the finite-volume and direct Gauss-Newton methods. We separate a spatially varying secondary field from the 1D background in time-domain, and constrain the calculation to be within the small volume of influence of airborne EM secondary source, resulting in more compact discretization...

Spectral-element (SE) method is a kind of higher-order finite-element method based on weighted residual technique; however, the basis functions for SE are polynomial, like Gauss-Lobatto-Legendre (GLL) or Gauss-Lobatto-Chebyshev (GLC) polynomials. Because of its high modeling accuracy and flexibility, it has been successfully used in computational e...

Mainstream numerical methods for 3D time-domain airborne electromagnetic (AEM) modeling, such as the finite-difference (FDTD) or finite-element (FETD) methods, are quite mature. However, these methods have limitations in terms of their ability to handle complex geologic structures and their dependence on quality meshing of the earth model. We have...

Traditional 3D Magnetotelluric (MT) forward modeling and inversions are mostly based on structured meshes that have limited accuracy when modeling undulating surfaces and arbitrary structures. By contrast, unstructured-grid-based methods can model complex underground structures with high accuracy and overcome the defects of traditional methods, suc...

We investigate an algorithm for 3D time-domain airborne electromagnetic (AEM) inversion based on the finite-volume (FV) method and direct Gauss-Newton optimization, where we obtain high efficiency by constraining the modeling volume to the AEM volume of influence (VOI) of a 3D source within the earth, rather than using the larger VOI of the AEM sys...

This paper presents a 3D forward modelling algorithm with an adaptive finite-element method based on unstructured grids that when used with a circular scanning DC measurement technique can provide an indication of anisotropy in a layered earth. The accuracy of this algorithm is checked against 1D semi-analytical solutions for an arbitrarily anisotr...